Oxygen is crucial for the human body because it fuels cells and provides the fundamental components needed for survival. It is essential for producing energy, building and replacing cells, and supporting the immune system. Oxygen helps cells combine with nutrients to produce proteins and carbohydrates, which are vital for energy and cell repair. Without oxygen, the body cannot sustain these processes, leading to severe damage and death within minutes of deprivation. More specifically, oxygen is vital for cellular respiration, where it helps produce ATP (adenosine triphosphate), the energy currency of cells. This energy is necessary for all bodily functions, including muscle movement, digestion, brain activity, and immune responses. Oxygen is carried through the blood by hemoglobin in red blood cells and is critical for keeping organs functioning properly, especially the brain and heart. Lack of oxygen can impair brain function, cause irritability, and in severe cases, result in brain damage and death within minutes. Additionally, oxygen supports the immune system by helping kill bacteria and supporting the cells that defend against infections. Oxygen deficiency can undermine these immune responses and overall bodily health. Maintaining proper oxygen levels through breathing and, when necessary, therapies like supplemental oxygen is essential for sustaining health and survival.